Speaker: Klaus Hermann, Fritz-Haber, Berlin
Date & Time: April 11, 2006 - 3:30pm
Location: Chemistry 260
Excitations and Reaction at Metal and Oxide Surfaces: cluster models can help to interpret experimental data
Laboratory for Surface Modification
Klaus Hermann, Fritz-Haber, Berlin
Chemistry 260, 3:30pm
This talk reviews recent theoretical work on electronic and structural properties of metal and oxide surfaces including adsorption and reaction of small molecules where density functional theory (DFT) and embedded surface cluster models have been used. Differently coordinated surface oxygen in vanadium oxides exhibits pronounced differences in its charging and binding, which influences the surface geometry and indicates different chemical behavior as identified by surface sensitive spectroscopies, PES, EELS, NEXAFS, and ELNES. Local binding becomes also evident from vibrational analyses performed for the surface clusters where frequencies and intensities can be used to interpret IR, Raman, and EELS spectroscopy data. Results from recent theoretical spectroscopy studies on vanadium sesquioxide, V2O3, and vanadium pentoxide, V2O5, will be discussed in detail and compared with experimental data.
Extended cluster studies on different phenylpropene adsorbates on Cu(111) substrate yield equilibrium geometries which are consistent with experimental findings based on angle-resolved NEXAFS measurements. In particular, the theoretical angle-resolved spectra evaluated in the cluster approach are in excellent agreement with all details of the experimental NEXAFS data. The comparison between theory and experiment can explain the different epoxidation rates of the adsorbates by simple geometric effects.